JPH0365762B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to concrete hollow cylindrical bodies such as concrete piles, pipes, poles, fume pipes or electrical wire pipes.

[Prior art]

Concrete hollow cylinders are generally made using the centrifugal molding method, which uses centrifugal force to compact the concrete. Specific methods of centrifugal molding include the wheel-tire method in which a cylindrical formwork is placed on a rotating drive wheel and the formwork is rotated, or the formwork is placed on a drive belt that runs on a cylindrical formwork. There is a belt system that rotates the

With the wheel-tire method, the formwork tends to vibrate when rotating;
It is not possible to apply a necessary amount of centrifugal force, the concrete material tends to separate, and a sufficient compaction effect cannot be obtained. As a result, there is a large difference in the wall thickness of the cylindrical body, resulting in the use of extra concrete.
In piles, etc., the inner diameter is small, causing inconveniences in construction such as the Nakahori method. Furthermore, during centrifugal molding, a large amount of slag (a water suspension of fine particles) was discharged from the inner surface of the product, making it impossible to fix and solidify the fine particles on the inner surface to form a smooth layer. The belt method also lacked ultra-high-speed rotation technology and there was no demand for such high speeds, so the resulting product had a rough, rough surface with no particulate layer fixed on the inner surface, similar to the wheel-tire method. In the end, no matter which method was used, the centrifugal force that could be applied to the concrete inside the column formwork was about 35G at most, so the compaction of the concrete was insufficient, causing pits and unevenness on the inner surface of the hollow. occurs in large quantities,
The quality was poor.

As mentioned above, the inner surface of conventional concrete hollow cylinders is made up of coarse particles and is not smooth. For example, in the case of humid pipes, after forming, stone powder, dry mortar, etc. are added manually, and the finishing is done with a trowel to form a smooth layer on the inner surface. It's growing. Additionally, electric wire pipes are buffed and polished after the product is completed.

[Purpose of the invention]

This invention was made in view of the above circumstances. The purpose is to have a smooth inner surface of a concrete cylinder with a compressive strength of 850 kg/cm ² or more, so that there is no need for smoothing treatment, and it is possible to insert objects into the hollow interior of piles, electric wire pipes, humid pipes, etc. for the hollow digging method. The purpose of the present invention is to provide a concrete hollow cylindrical body of extremely high quality suitable for use in passing through.

[Structure of the invention]

The present invention has achieved the above object by providing the following concrete hollow cylinder.

This concrete hollow cylinder is compacted by centrifugal force, has a solidified layer of solidified ultrafine particles on the inner surface of the hollow part, has a compressive strength of 850 kg/cm ² or more, and has a pit. It is characterized by a coefficient of 0.1 or less, a wall thickness difference of 2 mm or less, and a flatness of the inner surface of the hollow part of 0.1 mm or less.

Figure 1 shows a hollow cylindrical body made of concrete pile according to the present invention, and from the outside to the inside there are a concrete layer A, a mortar layer B, and a paste layer C, with ultrafine particles solidified on the inner surface. A solidified layer 2 is formed.

The ultrafine particles of this invention are ultrafine particles in concrete that aggregate on the inner surface of a cylindrical body during ultrahigh-speed centrifugal molding. The particle size is approximately 70% less than 50μ, approximately 30%
% is 50μ to 80μ, and the particles aggregate as a water suspension on the inner surface during molding, stick and solidify without flowing out, and form a smooth solidified layer with a thickness of 0.3 to 1.5 mm and a difference in unevenness of 0.1 mm or less. form. In addition, the cylindrical body formed in this way has a smooth inner surface with a difference in inner cylinder wall thickness of 2 mm or less at the same time as the solidified layer is formed. The difference in the cylindrical wall thickness of concrete piles made using the conventional wheel-tire centrifugal molding method is usually 9 to 15 mm, and the difference between the thicknesses t ₁ and t ₂ (t ₂ - t ₁ ) shown in Figure 2 is 9 to 15 mm. It is indicated by. Additionally, the pitt coefficient is 0.1
It is as follows. Here, pits 11 refer to voids or nests formed at the back of coarse aggregate in a concrete pile (see Figure 3a), and the number of pits N per concrete cross-sectional area A (cm ² ) is It is called Pitt coefficient N/A.

Figure 3 a shows the concrete pile of the present invention, with a diameter of 600φ, cross-sectional area A = 89.3 cm ² , number of pits N = 4,
Therefore, Pitt's coefficient is 0.045. Note that b in FIG. 3 is a conventional concrete pile made of wheel-tire type, with a diameter of 600φ, A=89.3cm ² , number of pits N=27, and a pit coefficient of 0.302.

Next, to explain the manufacturing method of this new concrete hollow cylinder, the mixing ratio of concrete was changed to cement (Portland cement) from 360 to 360.
400Kg/m ³ , fine aggregate 600~750Kg/m ³ , coarse aggregate 900~
1200Kg/m ³ , silica 50~200Kg/m ³ , water reducing agent 5~20
Kg/m ³ and water 130-170 Kg/m ³ of concrete is poured into a column forming form, and this is centrifugally formed using a belt-type centrifugal force column forming machine, preferably under 60 G or more for a certain period of time. .

Thereafter, it is pre-cured at 60-70°C for about 2-7 hours, and then autoclaved at 180-190°C and 10-12 atmospheres for about 8 hours.

This new concrete hollow cylindrical body can be stably obtained by centrifugal forming using a belt-type centrifugal force column forming machine under 60G or more.

The novel concrete hollow cylindrical body of the present invention cannot be obtained at about 35G as in the conventional case.

Next, the belt-type ultra-high-speed centrifugal column-making machine for producing concrete cylinders according to the present invention will be explained based on FIGS. 4 to 6. 1, 2 and
It consists of an auxiliary pulley 3, which is slightly smaller than the main pulleys 1 and 2 (approximately 70 to 80% larger than the main pulleys 1 and 2), and a flat belt 9, etc., stretched between these pulleys 1, 2, and 3. The flat belt 9 is configured to rotate at a high speed by rotating the main pulley using power such as the main pulley. The pulleys 1 and 2 and the sub-pulley 3 are installed at regular intervals in the diametrical direction of these pulleys.

The main pulleys 1 are attached to the shaft 4 at regular intervals in its longitudinal direction. When the shaft 4 is rotated at high speed by the power of a motor or the like, the main pulley can be rotated at high speed.

The main pulley 2 and the sub pulley 3 are arranged right side by side with the main pulley 1, and similarly to the main pulley 1, they are installed at regular intervals in the longitudinal direction of the shaft 4.

Further, the main pulley 2 and the sub pulley 3 are attached to brackets 5 and 6. The distance between the main pulley 2 and the sub pulley 3 can be freely adjusted by shifting the fixed position of the bearing 6 and the sub pulley 3 in the horizontal direction.

Furthermore, a parallel part 7 that continues in the circumferential direction is formed in the central part of the main pulleys 1, 2 and the sub pulley 3, and a tapered part 8 that tapers toward both ends of each pulley is formed on both sides of the parallel part 7. , 8 are formed respectively.

The flat belt 9 is formed by stacking one to a plurality of core materials made of nylon cloth vertically at a constant distance, and covering the surface with a cover rubber to a constant thickness.

The nylon cloth used as the core material is a plain weave made of nylon thread or nylon thread and various threads such as vinylon, tetron, and polypropylene.

In such a configuration, when the main pulley 1 is rotated at high speed by the operation of a motor or the like via the shaft 4,
The flat belt 9 rotates at high speed (circumferential speed 500 m/min to 200 m/min) while maintaining the shape of the meandering portion 9a between the main pulleys 1, 2 and the sub pulley 3.

Furthermore, when the column forming form 10 is placed horizontally on the flat belt 9 in advance, the column forming form 12 rotates at a high speed that easily exceeds the centrifugal force of 60 G due to the high speed rotation of the flat belt 9. Therefore, the concrete in the column forming form 10 can be centrifugally molded.

In this case, due to the shape of the pulley and the flat belt 9
Due to the structure, even if the rotational speed of the flat belt 9 is greatly increased, there is no danger that the flat belt 9 will meander, generate heat, or break.

When centrifugally forming concrete products, the centrifugal force G of the column forming form 12 is divided into about 3 to 5 stages. Then, the centrifugal force G is increased stepwise, and finally the centrifugal force G is set to 60 G or more for a certain period of time.

〔Example〕

Next, a specific manufacturing example of the concrete hollow cylindrical body of the present invention will be explained.

Portland cement 380Kg/m ² , fine aggregate 700
Kg/m ³ , coarse aggregate 1000Kg/m ³ , silica 120Kg/m ³ ,
A steel pipe form was filled with concrete mixed at a ratio of 12 kg/m ³ of water reducing agent and 150 kg/m ³ of water.

After that, this steel pipe formwork is rotated at high speed by the belt-type ultra-high-speed centrifugal force column forming machine mentioned above, and the centrifugal force is increased step by step until it reaches 50G, 60G, 70G,
Centrifugal molding was performed for 3 to 5 minutes at each step of 80G, 90G, and 100G.

Thereafter, it was pre-cured at 70°C for about 3 hours, and then autoclaved at 180°C and 10 atm for about 8 hours.

The various performances of the concrete compressive strength, pit coefficient, wall thickness difference, and flatness of the steel pipe concrete hollow cylindrical body centrifugally formed at each stage are shown in the graphs of FIGS. 7 to 10.

[Comparative example]

A steel pipe concrete cylindrical hollow body was manufactured by centrifugally molding for a predetermined period of time with only the final stage centrifugal force being 30G and 40G under the same manufacturing method as in the above example.

The compressive strength and other performances of the steel pipe concrete cylindrical hollow body are also shown in Figure 7~
This is shown in the graph of FIG.

The graph shows that the product according to the present invention is a concrete hollow cylindrical body that has extremely high compressive strength and has extremely small pit coefficient, wall thickness difference, and flatness compared to conventional products.

[Action and effect of the invention]

This invention consists of the above configuration. The inner surface of the hollow cylinder consists of a solidified layer of solidified ultrafine particles, and is extremely smooth.

The extremely small number of pits, less than 0.1, results in a dense cross-section, resulting in extremely high compressive strength of more than 850 kg/cm ² .

In addition, the compressive strength is extremely high, and the pitt coefficient, flatness, and wall thickness difference are extremely small, so the quality is extremely high.

Therefore, there is no need to finish the inner surface of this concrete hollow cylinder, and for example, when concrete piles are used in the hollow construction method, soil removal is efficient, and when electric wire pipes are used, there is little resistance when passing electric wires through. There is no risk of damaging electric wires, and when used in sewer pipes, it reduces the wall resistance of running water and increases the flow rate.

[Brief explanation of drawings]

Fig. 1 is a partially enlarged cross-sectional view of a concrete pile according to the present invention, Fig. 2 is a drawing explaining the difference in cylindrical cross section, and Fig. 3 a and b show pits of the concrete pile of the present invention and the conventional concrete pile. 4 and 5 are a front view and a plan view of a belt-type centrifugal force column forming machine for manufacturing concrete piles. FIG. 6 is a front view of a pulley, and FIG.
Figures 1 to 10 are graphs showing the relationship between centrifugal force G, compressive strength, Pitt coefficient, wall thickness difference, and flatness. A... Concrete layer, B... Mortar layer, C... Paste layer, D... Ultrafine particle coating layer, 1, 2... Main pulley, 3... Sub-pulley, 4...
...Shaft, 5, 6...Bearing, 7...Parallel part,
8...Tapered portion, 9...Flat belt, 10...Column formwork, 11...Pits.

Claims (1)

[Claims] 1. In a concrete hollow cylinder compacted by centrifugal force, there is a solidified layer of solidified ultrafine particles on the inner surface of the hollow part, and the compressive strength is 850 kg/
cm ² or more, a pitt coefficient of 0.1 or less, a wall thickness difference of 2 mm or less, and a flatness of the inner surface of the hollow part of 0.1 mm or less.